This article describes Phenergan’s dosages and strengths and gives details on how it’s given. You’ll also find information on savings and coupon options for Phenergan.
Phenergan is a brand-name medication. It comes as an injection that’s given deep into your muscle or into your vein. It’s available in a generic version called promethazine. This article describes dosages of Phenergan.
Boxed warnings
This drug has boxed warnings about the risks of fatal respiratory depression in children and serious tissue injury. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
For details, see the “Dosage of Phenergan” section below. See the end of this article for more information about these warnings.
Form and strengths of Phenergan
Phenergan comes as follows:
- Form: injection given deep into your muscle or into a vein
- Strengths: 25 milligrams per milliliter (mg/mL), 50 mg/mL
Dosage of Phenergan
This article describes the recommended dosages for Phenergan. The drugmaker provides these dosages.
If your doctor prescribes this medication, you should follow the dosage they prescribe. Your doctor will determine the dosage that best meets your needs.
Usual recommended dosages of Phenergan in adults
Phenergan is prescribed for several conditions. These include:
- allergic reaction
- sedation (to produce sleep)
- relief of nervousness
- nausea and vomiting related to certain types of anesthesia and surgery
- motion sickness
- pain after surgery
- sedation for surgery or labor and delivery
- certain surgical situations
Usually, doctors start by prescribing a low dosage of Phenergan. Then, they’ll adjust it over time until the right dosage is reached. Ultimately, your doctor will prescribe the smallest dosage of Phenergan that gives the desired outcome.
The following table outlines the recommended dosages of Phenergan for adults via injection deep into a muscle. Doses are in milligrams (mg).
| Condition or purpose | Recommended dose | Frequency |
| allergic reaction | 25 mg | single dose, may be repeated within 2 hours if needed |
| sedation | 25–50 mg | single dose |
| nausea and vomiting | 12.5–25 mg | single dose, not to be repeated more frequently than every 4 hours |
| use before or after surgery | 25–50 mg | single dose |
| labor and delivery | 25–50 mg | single dose, may be repeated one to two times every 4 hours during labor |
When given as an injection into your vein, the recommended maximum dose of Phenergan is 25 mg/mL and at a rate not to exceed 25 mg per minute.
Dosages of Phenergan in children
According to its prescribing information, the dosage of Phenergan for children ages 2 years and older should not be more than half of the recommended dosage for adults. The usual dosage is 1.1 milligrams (mg) per kilogram (kg) of body weight.
Note: Phenergan should not be given to children younger than 2 years old because it can cause serious and life threatening respiratory depression in children.*
* For details, see the end of this article for more information about this warning.
Dosage adjustments for Phenergan
Your doctor will prescribe a dosage of Phenergan based on several factors. These include:
- the specific condition being treated and how severe it is
- your age
- other health conditions you may have
Missed dose of Phenergan
If you need help remembering your appointment for your dose of Phenergan, you could try:
- downloading a reminder app on your phone
- setting an alarm
- putting a note where you’ll see it, such as on your calendar, bathroom mirror, or bedside table
Frequently asked questions
Below are answers to some commonly asked questions about Phenergan and its dosage.
How does the dosage of Phenergan compare with the dosage of Zofran?
Phenergan and Zofran are both prescribed for nausea and vomiting in certain situations. However, Zofran is no longer available as a brand-name medication. It’s still available in a generic version called ondansetron.
The following table outlines the recommended dosages of Phenergan and ondansetron injection for nausea and vomiting. The dosages are in milligrams (mg).
| Drug | Recommended dosage |
| Phenergan injection | 12.5–25 mg as a single dose, not to be repeated more frequently than every 4 hours |
| ondansetron injection | 4 mg as a single dose |
Ondansetron is also available as oral tablets and a liquid form that you swallow.
If you have questions about which treatment option is right for you, talk with your doctor.
Is Phenergan prescribed long term?
No, doctors don’t usually prescribe Phenergan injections as a long-term treatment. Instead, they are usually prescribed for short-term treatment.
If you have questions about how often you will receive Phenergan injections, talk with your doctor.
How Phenergan is given
Your doctor or another healthcare professional will give you Phenergan. It may be injected deep into your muscle or by intravenous (IV) infusion (an injection given into your vein over time).
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Get free cardWhat to ask your doctor
This article describes the usual recommended dosages for Phenergan. If your doctor prescribes this medication, they’ll determine the dosage that’s best for you.
Let your doctor know if you have concerns or questions about your treatment plan.
Here’s a list of some possible questions you may want to ask your doctor:
- How many doses of Phenergan will I need?
- How long after a dose of Phenergan will I start to feel better?
- How does a dose of Phenergan compare with doses of other medications prescribed for my condition?
Boxed warnings for Phenergan
This drug has boxed warnings about the risks of fatal respiratory depression in children and serious tissue injury. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
Risk of respiratory depression in children. Phenergan should not be given to children under age 2 years old. Doing so can cause slowed and shallow breathing that can lead to death. Due to this risk, Phenergan should be given with caution to children ages 2 years old and over.
Risk of serious tissue injury. Phenergan can cause severe irritation and damage to your tissues. This can cause symptoms such as burning, pain, swelling, and discoloration. In some cases, this damage can lead to tissue death and even amputation.
To lower this risk, Phenergan should be injected deep into your muscle. It may also be injected into a vein. Phenergan should not be injected under your skin.
For details, see the “Dosage of Phenergan” section above. You can also talk with your doctor to learn more.
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.